A camshaft of a valvetrain may control motion of a poppet valve, such as an intake or an exhaust valve in an engine. In addition to the valves and the camshaft, the valvetrain may also include rocker arms, pushrods, and lifters that couple the valves to the camshaft and translate rotational motion of the camshaft into linear motion of the valves. The components of the valvetrain may work in concert to control amounts of air and fuel delivered to a combustion chamber during engine operation. Lifting of the intake valve allows the air to enter the combustion chamber through an inlet port and, when released by the cam, the intake valve may close and block air flow. Similarly, when the exhaust valve is lifted, exhaust gas may flow from the combustion chamber to an exhaust manifold through an outlet port. The intake and exhaust valves may be adapted with a valve spring to seal the valve against a valve seat when adjusted to closed positions by the cam.
The valve spring may coil around a valve stem of the intake or exhaust valve between a cylinder head surface and a valve spring retainer. In an overhead camshaft orientation, the valve may be depressed by the cam, thereby compressing the valve spring and opening the valve. When closed, a spring load of the valve spring exerts pressure against the cylinder head surface and against the valve spring retainer to press the valve against the valve seat and block flow through the inlet or outlet port of the cylinder. To counter the spring load of the valve spring, a valve spring retainer may be arranged along the valve stem at an opposite end of the valve from the valve seat, resisting the force exerted by the valve spring so that the valve spring retainer is not displaced. In this way, the valve spring retainer may be anchored along the valve while expansion of the valve spring compels the valve to slide upwards into the closed position.
The spring load of the valve spring may depend upon an overall mass of the valvetrain. Components of the valvetrain, including the valve spring retainer, are typically formed from a durable, heat-resistant material, such as steel. Forming the valvetrain parts from a metal, however, may result in a heavy mass of the valvetrain and the spring load of the valve spring may be increased accordingly in order to maintain contact between the valve and a cam lobe of the camshaft. This may also increase friction within the valvetrain and lead to degradation of components. In particular, a positioning of the valve spring retainer at a top of the valve stem of either the intake or exhaust valve may increase stress on the valve.
Attempts to reduce the weight of the valvetrain include decreasing a mass of the valve spring retainer. One example approach is shown by Black in U.S. Pat. No. 4,321,894. Therein, a valve spring retainer is disclosed with a base that includes an aperture. The base also has a lip that projects downward to fit over and retain a valve spring. The valve spring retainer further includes a valve adjuster cap with threading that engages with threading in the base. Both the base and the adjuster cap are formed from thinner surfaces and less material than conventional, solid valve spring retainers. Thus an overall mass of the valve spring retainer is reduced.
However, the inventors herein have recognized potential issues with such systems. As one example, forming the valve spring retainer from two individual pieces, e.g., the base and the adjuster cap, increases a number of parts to be manufactured, thus raising production costs. In addition, by doubling the number of components of the valve spring retainer, labor and assembly time is increased for fabrication of the valve spring retainer.
In one example, the issues described above may be addressed by a valvetrain of an engine comprising a valve spring, a disc-shaped valve spring retainer having a central aperture and a plurality of inner cavities concentric with the central aperture, the retainer engaging with a first end of the valve spring. In this way, the valve spring retainer may be manufactured in a cost-effective manner as a single, unitary component with a reduced mass.
As one example, the valve spring retainer may be adapted with internal cavities so that the valve spring retainer is at least partially hollow. The internal cavities may form rings of air within a thickness of the valve spring retainer, with air inside the cavities coupled to air surrounding the valve spring retainer through channels. As a result of the hollow configuration, an amount of metal used to form the valve spring retainer is significantly reduced without affecting a structural integrity of the valve spring retainer. The retainer may be fabricated as a single unit by additive manufacturing, thus reducing production labor and time.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.